This invention relates to cable television (CATV) and, more particularly, to an economical wide-bandwidth system for distributing CATV signals to multiple customers.
Proposals have been made to utilize an optical fiber as the transmission medium for carrying multiple-channel CATV signals from a source to a distant remote terminal (RT) from which the signals are in turn distributed to multiple customers. Such a wide-bandwidth medium, commonly referred to as a supertrunk, typically requires a relatively expensive laser at the source and a relatively expensive optical detector at the RT. But since the RT is designed to distribute the CATV signals in parallel to many customers, the shared cost per customer of these expensive components is in practice acceptably low.
Heretofore, the multiple-channel CATV signals delivered to the RT have in effect simply been retransmitted to each of the customers by the RT. In other words, the transmission medium between the RT and each customer carries the total set of channels provided by the CATV signal source. In turn, each customer is provided at his premises with a TV tuner with which he locally selects for viewing one of the multiple channels transmitted to him from the RT.
Conventional CATV distribution systems typically utilize coaxial cable to transmit the multiple-channel signals from the RT to customers. Although some proposals have been made to employ a dedicated wide-bandwidth optical fiber between the RT and each customer, these proposals have not generally been regarded as economically feasible. This is so because the cost of the laser and detector that would be required per RT-to-customer fiber to achieve satisfactory signal performance in such a distribution system is in practice extremely high. If lower-quality lower-cost lasers were used to transmit the multiple-channel CATV signals from the RT, the signals received by customers would generally be of unacceptable quality, due to inherent laser noise, intermodulation noise among the channels and a low modulation index per channel.
Accordingly, considerable efforts have been directed by workers skilled in the art aimed at trying to design an economically feasible CATV distribution system that includes an optical fiber path between an RT and each customer served thereby. It was recognized that these efforts, if successful, could provide a practical high-quality system capable of economically distributing CATV, and other, signals to multiple customers.